Abstracts

Rationale: Seizures in Tuberous Sclerosis Complex (TSC) start in early childhood and over 50% will evolve into medically refractory cases often featuring mental retardation and behavioral issues. In these cases, early surgery might be the only treatment. Conventional non-invasive presurgical procedures often confuse the identification for surgery candidacy of brain areas involved in epileptogenesis. Methods: Presurgical evaluation was performed in 11 drug resistant TSC patients, 10 between 1 and 5 years of age and one adult, including ictal and interictal scalp EEG video-monitorization, Magnetic Resonance Imaging (MRI) and Positron Emission Tomography(PET) in some case. Magnetoencephalography (MEG) was performed initially in 9 patients but was not considered for decision making. Surgical excision was performed after determination of ictal site with depth electrode videomonitoring. Patients who did not achieve Engel I classification of postoperative outcome underwent a second presurgical evaluation, MEG evaluation and epilepsy surgery. A new Engel classification was registered for them. MEG contribution to presurgical evaluation was retrospectively assessed. Results: Ictal scalp EEGs were multifocal or non-localizing in all but 2 patients. MRI and PET revealed multiple bilateral lesions and hypometabolic regions. 5/11 patients became seizure free after a first surgery, all of which had ictal temporal locations; MEG was concordant or partially concordant with ictal depth electrode localization in all 5 patients. 4/11 patients were classified as Engel III-IV after surgery and had multifocal ictal intracranial EEG locations; MEG was not done in 2 and was concordant with surgical excision in another 2. After a second surgical procedure in these, only 1 patient became seizure free. The remaining 2 patients of the series have not been operated yet. Conclusions: Presurgical MEG unifocal temporal locations are prone to Engel I outcome after surgery in TSC despite non-conclusive scalp EEG and imaging data. Multifocal MEG would blur sugery outcome prognosis, however a worthwhile improvement might be achieved. MEG inclusion in systematic presurgical evaluation of TSC could help plan intracranial EEG and predict surgery outcome in TSC.